这个例子还是由四个文件组成
html源文件清单
<html>
<head>
<!--
Date: 2018-3-19
Author: kagula
Description:
相对于上一个例子
[1]去掉了透视投影变换.
[2]添加了纹理显示
[3]添加了打印投影后的纹理数据.
Original:
[1]《利用WebGL2 实现Web前端的GPU计算》
https://my.oschina.net/thesadabc/blog/1592866
測試環境
[1]Chrome 65.0.3325.162
[2]nginx 1.12.2
-->
<title>我的第三个Webgl2演示</title>
<meta charset="utf-8">
<!-- gl-matrix version 2.4.0 from http://glmatrix.net/ -->
<script type="text/javascript" src="/gl-matrix-min.js"></script>
<script type="text/javascript" src="/kagula/webgl2_helper.js"></script>
</head>
<body>
<canvas id="glCanvas" width="320" height="200"></canvas>
</body>
</html>
<script>
main();
//弄4个顶点, 用来演示render流程!
function initBuffers(gl) {
// Create a buffer for the square's positions.
const positionBuffer = gl.createBuffer();
// Select the positionBuffer as the one to apply buffer
// operations to from here out.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Now create an array of positions for the square.
//WebGL最后会把计算好的图像信息投影到左下角{-1,-1}，右上角{1,1}的区域中。
const positions = [
1.0, 1.0,
-1.0, 1.0,
1.0, -1.0,
-1.0, -1.0,
];
// Now pass the list of positions into WebGL to build the
// shape. We do this by creating a Float32Array from the
// JavaScript array, then use it to fill the current buffer.
gl.bufferData(gl.ARRAY_BUFFER,
new Float32Array(positions),
gl.STATIC_DRAW);
return {
position: positionBuffer
};
}
async function main() {
//选择器的使用
//http://www.runoob.com/jsref/met-document-queryselector.html
const canvas = document.querySelector("#glCanvas");
// Initialize the GL context
//為了获取WebGL2上下文,getContext方法传入的参数是"webgl2",而不是"webgl".
const gl = canvas.getContext("webgl2");
// Only continue if WebGL is available and working
if (!gl) {
alert("Unable to initialize WebGL. Your browser or machine may not support it.");
return;
}
//OpenGL ES 3.0 不支持多维数组
//對傳入的數組大小有限制
console.log("gl.MAX_VERTEX_UNIFORM_VECTORS=" + gl.MAX_VERTEX_UNIFORM_VECTORS + ", gl.MAX_FRAGMENT_UNIFORM_VECTORS=" + gl.MAX_FRAGMENT_UNIFORM_VECTORS);
//装配shader到shaderProgram中去
const vsSource = await loadResource("../shader/simple.vs");
const fsSource = await loadResource("../shader/simple.fs");
const shaderProgram = initShaderProgram(gl, vsSource, fsSource);
//为了让外部的数据能统一传到shanderProgram中去，新建programInfo对象。
//vertexPosition => aVertexPosition位置
//projectionMatrix => uProjectionMatrix位置
//modelViewMatrix => uModelViewMatrix位置
//...
const programInfo = {
program: shaderProgram,
attribLocations: {
vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition')
},
uniformLocations: {
samplerA: gl.getUniformLocation(shaderProgram, 'samplerA')
},
};
//initBuffers(gl)返回要render的vertex.
drawScene(gl, programInfo, initBuffers(gl));
}//main
</script>
webgl2_helper.js
async function loadResource(remoteFile) {
try {
let response = await fetch(remoteFile);
return response.text();
console.log(data);
} catch(e) {
console.log("Oops, error", e);
}
}
// Initialize a shader program, so WebGL knows how to draw our data
function initShaderProgram(gl, vsSource, fsSource) {
const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
// Create the shader program
const shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
// If creating the shader program failed, alert
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));
return null;
}
return shaderProgram;
}
// creates a shader of the given type, uploads the source and
// compiles it.
function loadShader(gl, type, source) {
const shader = gl.createShader(type);
// Send the source to the shader object
gl.shaderSource(shader, source);
// Compile the shader program
gl.compileShader(shader);
// See if it compiled successfully
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
return null;
}
return shader;
}
function drawScene(gl, programInfo, buffers) {
gl.clearColor(0.0, 0.0, 0.0, 1.0); // Clear to black, fully opaque
gl.clearDepth(1.0); // Clear everything
gl.enable(gl.DEPTH_TEST); // Enable depth testing
gl.depthFunc(gl.LEQUAL); // Near things obscure far things
// Clear the canvas before we start drawing on it.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
//這裏準備vertex shader需要的數據
//整個pipeline可以看成下面的流程
//我們使用WebGL準備數據 => Vertex Shader => WebGL => Fragment Shader => WebGL => Canvas
// Tell WebGL how to pull out the positions from the position
// buffer into the vertexPosition attribute.
{
// gl.ARRAY_BUFFER => 指向 => buffers.position
gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
//指定源数据格式.
//https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/vertexAttribPointer
gl.vertexAttribPointer(
programInfo.attribLocations.vertexPosition,
2,// pull out 2 values per iteration //Must be 1, 2, 3, or 4. 比如说顶点{x,y}要选2，{x,y,z}要选3，颜色{r,g,b,a}要选4
gl.FLOAT,// the data in the buffer is 32bit floats
false,// don't normalize
0,//stride, how many bytes to get from one set of values to the next
0);//how many bytes inside the buffer to start from
//源数据填充到gl
//tell WebGL that this attribute should be filled with data from our array buffer.
//gl.ARRAY_BUFFER => 数据传到 => programInfo.attribLocations.vertexPosition
gl.enableVertexAttribArray(
programInfo.attribLocations.vertexPosition);
}
// Tell WebGL to use our program when drawing
gl.useProgram(programInfo.program);
//准备fragment shader要用到的纹理数据，并把它传入到webGL中。
{
function initTexture(index, pixels) {
let dim = 3;//3*3 size 大小纹理。
const texture = gl.createTexture();
gl.activeTexture(gl[`TEXTURE${index}`]);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);//如果没有这行代码，WebGL会采用“插入过渡颜色”来进行纹理映射。
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, dim, dim, 0,
gl.RGBA, gl.UNSIGNED_BYTE, pixels, 0);
gl.uniform1i(programInfo.uniformLocations.samplerA, index);
}
const colorMap = new Uint32Array([
0xFF0000FF, 0x00FF00FF, 0x0000FFFF,
0xFFFF00FF, 0xFF00FFFF, 0x00FFFFFF,
0x000000FF, 0xFFFFFFFF, 0xF0F0F0FF,
]);
const RGBAMap = new Uint8Array(colorMap.buffer);
initTexture(0, RGBAMap);
}
//數據準備好后可以draw了.
{
const offset = 0;
const vertexCount = 4;
//开始处理已经在gl中的顶点数据
//gl.TRIANGLE_STRIP模式復用前面兩個頂點, 所以這裏告訴gl, render兩個三角形.
gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
}
{
const canvas = document.querySelector("#glCanvas");
let picBuf = new ArrayBuffer(canvas.width * canvas.height * 4);
let picU8 = new Uint8Array(picBuf);
let picU32 = new Uint32Array(picBuf);
//void gl.readPixels(x, y, width, height, format, type, ArrayBufferView pixels, GLuint dstOffset);
//x A GLint specifying the first horizontal pixel that is read from the lower left corner of a rectangular block of pixels.
//y A GLint specifying the first vertical pixel that is read from the lower left corner of a rectangular block of pixels.
//width A GLsizei specifying the width of the rectangle.
//height A GLsizei specifying the height of the rectangle.
//format A GLenum specifying the format of the pixel data. Possible values:
// gl.ALPHA: Discards the red, green and blue components and reads the alpha component.
// gl.RGB: Discards the alpha components and reads the red, green and blue components.
// gl.RGBA: Red, green, blue and alpha components are read from the color buffer.
//type A GLenum specifying the data type of the pixel data. Possible values:
// gl.UNSIGNED_BYTE
// gl.UNSIGNED_SHORT_5_6_5
// gl.UNSIGNED_SHORT_4_4_4_4
// gl.UNSIGNED_SHORT_5_5_5_1
// gl.FLOAT
//pixels An ArrayBufferView object to read data into. The array type must match the type of the type parameter.
// Uint8Array for gl.UNSIGNED_BYTE.
// Uint16Array for gl.UNSIGNED_SHORT_5_6_5, gl.UNSIGNED_SHORT_4_4_4_4, or gl.UNSIGNED_SHORT_5_5_5_1.
// Float32Array for gl.FLOAT.
//具体参考
//https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/readPixels
gl.readPixels(0, 0, canvas.width, canvas.height, gl.RGBA, gl.UNSIGNED_BYTE, picU8);
console.log(picU32);
}
}
simple.vs
#version 300 es
//指定float int的精度
precision highp float;
precision highp int;
//從設備外部传入的數據.
in vec4 aVertexPosition;
out vec2 frag_vpos;
void main() {
//从{左下角,右上角}={(-1,-1),(1,1)}转到{左下角,右上角}={(0,0),(1,1)}
frag_vpos.x = (aVertexPosition.x + 1.0)/2.0;
frag_vpos.y = (aVertexPosition.y + 1.0)/2.0;
//vertex shader输出的坐标是以canvas中心为(0,0) 水平向右为x轴正方向 垂直向上为y轴正方向 两轴的取值范围为[-1, 1]
gl_Position = aVertexPosition;
}simple.fs
#version 300 es
precision highp float;
precision highp int;
in vec2 frag_vpos;
uniform sampler2D samplerA;
//output to pipeline
out vec4 myOutputColor;
void main() {
vec4 color = texture(samplerA, frag_vpos);
myOutputColor = color.abgr;
}